GRID-CONNECTED WIND TURBINE SYSTEMS

For many years now small-scale domestic and commercial WIND TURBINE grid connected systems have proven themselves to be increasingly viable means of generating clean electricity AND providing a steady income.
After much negotiating with both DTI and electricity distribution companies during the last few years it has been agreed that turbines up to 6KW can be very easily connected to the grid to export electricity and receive an income. The (hard fought for) G83/G59/G99 recommendation gives anyone permission (hassle free) to connect a generator to the national grid provided it has been type tested.

As with PV systems the system owner was paid both for the total electricity generated AND for any exported using special export meter (Feed In Tariff). Instead of exporting you can ‘dump’ any surpus power into heating and thus both reduce heating bills AND heat your house with renewables!

In order to connect in parallel to your existing supply a special wind inverter is used to synchronise the varying voltage from the turbine to the stable grid supply. This G99 approved inverter is designed and built in Europe, and individually programmed on-site to optimise the amount of power exported to the grid using complex algorithms as well as ensuring network safety by disconnecting if the grid fails or becomes unstable. The inverter is also able to power the house during a power cut in conjunction with a battery back-up system, otherwise the turbine is left to ‘free wheel’ harmlessly until the power is resumed.

Solar systems from Sustainergy

PHOTOVOLTAIC MODULES

Otherwise known as PV’s or SOLAR PANELS; these are rectangular flat devices that face the sun and generate electric power from its light. The energy of photons is used to energise electrons in the PV’s laminations). Three types of PV cells exist;

• Mono-crystalline;
• Poly-crystalline and;
• Amorphous.

“Mono’s” are the smallest cells and they generally last a little longer. Poly’s are slightly larger, whilst Amorphous cells cope well with high temperatures but are significantly larger and have a shorter life-span (they are, however, slightly cheaper).

A PV array is generally easy to install and the modular nature of such a system allows for easy additions later on. A south facing roof of any pitch is ideal. The solid state technology employed in the production of PV’s means that they are very reliable, lasting 30+ yrs.

If PV’s on their own have a drawback it is that they generate most power in the summer when it is not always needed, and less power in winter when needs are often greater. For this reason PV systems are often appropriately used on a seasonal basis (summer holidays) or incorporated as part of a WIND/PV hybrid system. Where cost is not so important a PV only system will provide year round power, however the number of modules, and hence cost, will be significantly greater. Planning permission is not usually required for PV’s.

The most common and least expensive PV systems consist of a PV array ‘bolted on’ to the roof, this means that it stands up slightly proud of the roof. More integrated systems involve removing the slates or tiles, fixing the array to the rafters and then re-fitting the slates/tiles around the array forming a waterproof barrier (similar to a Velux roof window). Also available, though more expensive, are ‘Solar Slates/Tiles’ which mimick the look of normal slates/tiles – though these integrated systems cost more.

Typically, in Southern UK, 4 KW of PV panels (8m x 3.5m) will generate about 4,000KWh (units) of solar electricity per year – a 2KW system will produce half…

Typical costs (through SUSTAINERGY) are in the region of £800 per KW including installation.

Site-assessment visits should be arranged prior to ordering: We will come and look at your roof and house, chat to you informally and prepare a quote for an appropriate PV system – just phone us!

Solar PV grid connected system

For many years now small-scale domestic and commercial Solar PV grid connected systems have begun to emerge as increasingly viable demonstrations of how future energy generation may occur….read on and prepare for the future (or the present if you are enthusiastic enough).

A renewable generator, such as PV Solar, can be connected to the national grid in most countries. Also, when a solar PV array is connected to the grid you can get paid for producing solar energy – currently this is for the exported energy only.

It works like this: Light from the sun (either directly or through thin clouds) hits the solar panels and is converted into DC electricity. With grid-connected systems the DC electricity is fed, via two small cables and an isolating switch, to a special inverter. This compact and quiet DNO approved inverter transforms the DC electricity into an exact replica of the AC grid-electricity and sends electrical power to the house circuits and back to the national grid (if there is surplus). An electricity meter measures how much solar electricity is being generated so that it can be sold.

Typically, in Southern UK, 4 KW of PV panels (8m x 3.5m) will generate about 4,000KWh (units) of solar electricity per year – a 2KW system will produce half…

Typical costs (through SUSTAINERGY) are from of £8000 per KW including installation. A typical 4KW system is around £4,000 installed.

Most roofs are suitable, providing they face between East, South, and West – optimum pitch is between 20-60 degrees. Roof material is not a problem – the PV array is secured (with 125mph loading tests) to special aluminium rails that are screwed to the roofs rafters through the slate/tile/shingle/concrete etc. Strict attention is paid to continuity of weatherproofing. Alternatively the whole array can be integrated into the roof – like a Velux roof window.

The whole PV system has a basic 2 year warranty, with 10 year full guarantee on the mounting structure, and the PV modules 25 years! The system has a life expectancy of over 35 years… Maintenance on PV systems (unlike WIND systems) is absolutely minimal – gentle washing of the PV glass and possible inverter service.

SUSTAINERGY were one of the first MCS accredited installers and thus have passed a strict quality control criteria. Local councils also contract us to install on remote public buildings.

OFF-GRID (BATTERY) SYSTEMS

Mostly suitable for locations that are not connected to the national electric grid, off-grid (or stand-alone) systems store spare energy, generated from wind/solar/hydro etc, in a large battery bank. During periods of insufficient generation the battery then provides the power needed (for lights and appliances etc).

Battery systems tend to cost 10-20% more than grid-connected ones – mainly because of battery cost (and 10 yearly replacement) and sophisticated charging controllers.

However, well designed and installed systems are very reliable and usually no different to the consumer than conventional grid-connected buildings.

As all battery systems are tailor-made for each individual customer, more discussion is necessary between yourselves and our engineers – please check through the Your energy needs page and read it carefully, then download the load-table document and fill it in as best you can – you will probably need to CONTACT US for help with this.

A battery system must have a weather-proof room to house all the equipment that will manage the power. This room can be within a house or outside (shed), and it is often called the ‘powerhouse‘. The powerhouse will usually hold the following equipment: Large bank of batteries (in sealed box), large DC fuses/disconnects, charge controller (regulates battery voltage), dump heater, large inverter (transforms battery voltage into normal mains 240V), energy display meters, automatic generator start controller and AC fusebox. These are usually fixed to a plywood board attached to the wall – preferably out of childrens reach.

All this equipment contains complex and expensive electronics and so should NOT be kept in humid or damp places – condensation (common with tin roofs) should also be avoided.

When the battery bank becomes full, the charge controller will often need to divert the incoming energy to a dump heater or two – this could be an immersion or a storage heater. These can be installed in the powerhouse but are more useful in a living space – there’s great satisfaction felt when these heaters come on, warming you up and telling you that the batteries are full!

The batteries are usually installed in an insulated plywood box (or similar) with two vent pipes taking the explosive/corrosive hydrogen gases outside. Fuses and disconnects will be installed close to the battery for protection and the large cables will then connect up the charge controller and inverter.

A typical powerhouse set-up would look like this (battery is adjacent):

Calculating your energy needs

The first step in designing a Renewable Energy System is to appreciate that it is easier and more economic to reduce consumption through energy efficient appliances, than it is to generate more power. The government has introduced an energy labelling scheme which labels all appliances with their efficiency rating (A-G), always buy ‘A’ rated appliances.

A typical preparatory measure then, might be to install energy efficient lighting or exchange electrical heating appliances with alternatives (e.g. gas/wood). Spending pennies here will save pounds later.
Next you need to examine in detail where your power will be going, and attempt to reduce this to an acceptable, but comfortable minimum. In order to assess individual power needs a form, to be filled in, is included in this document.

To complete the “Load Assessment Table” first make a list of electrical appliances that make up the Load (i.e. anything electrical in your house).
For small systems, using more efficient 12 volt DC appliances is generally better than their 240 volt ac counterparts (even though the initial purchase of a 240 volt appliance is usually cheaper). These can be lights, laptops, printers, fridges, travel kettles etc. Also heavy duty 12 volt power tools are readily available. With part or whole DC systems, make a seperate list of DC and AC appliances.For larger systems (e.g. conventional house), a quality high power inverter transforms the battery power into ‘normal’ mains 240 volt AC, and feeds into the house cicuits (sockets and lights etc) exactly as normal. This inverter needs to be sized to match your energy needs, though expansion is often possible later on should situations change. For pure 240V AC systems you only need to fill in the AC section of the table.

Next to each appliance write its POWER CONSUMPTION. This may vary widely between similar appliances. This figure is normally found on a data-plate on the back of the appliance. The given figure will be the maximum value, not the average, so it is usually appropriate to reduce this value somewhat. A list showing approximate values for popular appliances can be supplied on request – this can help you fill out the form.
The next column is the HOURS OF USE per day for each appliance. Ideally this should be done for every month of the year as seasonal variations are important, however for simplicity: Mid-summer and mid-winter values will suffice. Please note that refrigerators and freezers are only actually on for about 12 hours a day in the summer and 8 hours in winter.

If the POWER CONSUMPTION and HOURS OF USE column are multiplied together the result is the DAILY CONSUMPTION, expressed in watt-hours. This is the most important column, in that it shows how much ENERGY is being used by each individual appliance, indicating which are the most demanding (and expensive to run) overall.
Click on loadtable (download…) to download a spreadsheet which you should fill in and email back to us. Once we receive your form we can start to design (without any cost to you) an appropriate renewable energy system tailored to your individual ENERGY NEEDS.

BATTERIES

Storage batteries (for Off-Grid systems) store and regulate the electrical power as it is generated by the sun or wind, and also as it is used to power appliances around the house. Many myths surround these necessary lumps of lead and acid – some of which are are explained below. For Lithium batteries skip to the bottom…

For any stand-alone renewable energy system, (where electrical input is dependant on slightly random variables e.g. wind/sun/water etc), the large bank of storage batteries MUST be genuine deep-cycle cells. This does NOT include cheaper car or ‘leisure’ batteries which simply will not last very long.

The problem is that with a stand-alone system the battery bank will be drained (or cycled) down to a low state of charge regularly – thus it is essential that the battery will not be damaged by this cycling effect. Deep-cycle batteries are specially designed to cope with this, where-as car and ‘leisure’ batteries are not (fork-lift batteries are also suitable).

The result is that you will have to replace the battery FAR sooner if deep-cycle cells are not used, and the overall long term expense will be much greater (this doesn’t mean that you can’t experiment and have fun with second hand batteries, but don’t expect a lifetime out of them).

Most storage batteries are of a Lead-Acid content – they have thick lead electrolytic plates surrounded by sulphuric acid. These cells come in all shapes and sizes – usually individual 2 volt cells or 6 volt triple cells. These cells progressively deteriorate both with age and more importantly with regular deep discharging. However it is necessary to discharge the cells in order to use them as storage, the point is to minimise the effect that this causes. This involves buying quality batteries and looking after them appropriately (see below).

We currently use Rolls and Trojan cells, as we believe they are high quality, tested cells available at a reasonable price (Trojan are the number one deep-cycle battery in the US), Rolls are used extensively by the renewables industry and they actually guarantee their battery!. The storage battery is an expensive part of the installation and we use the best we can get within an acceptable budget.

In order to look after your batteries properly you need to be constantly aware of their state of charge (SOC) – just like checking how much petrol is in your car. An accurate SOC ‘fuel’ gauge is installed which monitors exactly how much charge goes in and comes out of the batteries and displays exactly what your SOC is (they can also sound an alarm or switch on a generator at a programmed SOC – e.g. 50%).

A simple glance at the SOC guage once a day will let you know whether you have plenty of spare power (washing day!) or whether you are low on power (reduce your load). Often charge controllers and inverters use green and red LED lights to show the state of the battery but these are inaccurate guages and no substitute – they simply look at the voltage not the SOC.

Inevitably batteries will get deeply discharged to 30 or 40% SOC from time to time (when you use extra power or if its not very windy or sunny for several days). Some of the damage that this causes can be rectified by regular equalisation charging of the cells – this is when you slightly over-charge them by raising the voltage above normal, causeing them to ‘gas’ and bubble, which has the effect of cleaning the built up sulphur off the plates. Normally you should perform an equalisation charge once per month for two hours, and most inverters will do this either automatically or at a push of a button.

Lithium Ion: These modern batteries are slowly replaceing Lead-Acid types, as they have many signficant advantages: They don’t suffer from regular deep-cycling and draining, they are smaller and lighter, they don’t give off dangerous gases, they usually last longer. Unfortunately they are still around FOUR times as expensive as the lead-acid equivalent, though the price is dropping every year.